Ultrafast Photoconversion Dynamics of the Knotless Phytochrome SynCph2

The family of phytochrome photoreceptors contains proteins with different domain architectures and spectral properties. Knotless phytochromes are one of the three main subgroups classified by their distinct lack of the PAS domain in their photosensory core module, which is in contrast to the canonical PAS-GAF-PHY array. Despite intensive research on the ultrafast photodynamics of phytochromes, little is known about the primary kinetics in knotless phytochromes. Here, we present the ultrafast Pr ⇆ Pfr photodynamics of SynCph2, the best-known knotless phytochrome. Our results show that the excited state lifetime of Pr* (~200 ps) is similar to bacteriophytochromes, but much longer than in most canonical phytochromes. We assign the slow Pr* kinetics to relaxation processes of the chromophore-binding pocket that controls the bilin chromophore’s isomerization step. The Pfr photoconversion dynamics starts with a faster excited state relaxation than in canonical phytochromes, but, despite the differences in the respective domain architectures, proceeds via similar ground state intermediate steps up to Meta-F. Based on our observations, we propose that the kinetic features and overall dynamics of the ultrafast photoreaction are determined to a great extent by the geometrical context (i.e., available space and flexibility) within the binding pocket, while the general reaction steps following the photoexcitation are most likely conserved among the red/far-red phytochromes.

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The mechanism of the photochemical cycloaddition reaction of N-benzoylindole with cyclopentene

Canadian Journal of Chemistry ◽

10.1139/v90-262 ◽

1990 ◽

Vol 68 (10) ◽

pp. 1685-1692 ◽

Cited By ~ 10

Author(s):

Bimsara W. Disanayaka ◽

Alan C. Weedon

Keyword(s):

Excited State ◽

Quantum Yield ◽

Ground State ◽

Mechanistic Model ◽

Cycloaddition Reaction ◽

Intersystem Crossing ◽

Triplet Excited State ◽

Excited State Lifetime ◽

Yield Data ◽

Counting Procedure

The mechanism of the photochemical cycloaddition reaction between N-benzoylindole, 1, and cyclopentene to give cyclobutane adducts 2 and 3 has been examined. The triplet excited state lifetime and quantum yield of intersystem crossing were determined for 1 as (2.8 ± 0.3) × 10−8 s and 0.39 ± 0.01, respectively, using the triplet counting procedure. In addition, the dependence of the quantum yield of cycloadduct formation upon the concentration of cyclopentene and upon the concentration of excited state quenchers has been determined. The results are used to propose a mechanistic model in which the triplet excited state of 1 reacts with cyclopentene to give a triplet 1,4-biradical intermediate. Following spin inversion the biradical intermediate reverts to the ground state starting materials or proceeds to the products 2 and 3; this partitioning, along with the quantum yield of intersystem crossing, gives rise to a limiting quantum yield of cycloaddition at infinite alkene concentration of 0.061. It is calculated that 84% of the biradical intermediates revert to the starting materials and 16% proceed to cycloadducts. The quantum yield data are also used to calculate two independent values of the rate constant for reaction of the triplet excited 1 with alkene; the values are (1.8 ± 0.1) × 107M−1 s−1 and (4.0 ± 0.8) × 106 M−1 s−1'. Some evidence for self quenching of the triplet excited state of 1 by ground state 1 was also observed. The quantum yield of intersystem crossing and the triplet excited state lifetime of 1 were found to vary with the solvent used; this is discussed in terms of the possible existence of a charge transfer triplet excited state. Keywords: indole, photocycloaddition, mechanism.

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Computer Simulations of Viscosity Dependent Molecular Relaxation Processes

Laser Chemistry ◽

10.1155/lc.5.119 ◽

1985 ◽

Vol 5 (3) ◽

pp. 119-132 ◽

Cited By ~ 12

Author(s):

M. Kaschke ◽

J. Kleinschmidt ◽

B. Wilhelmi

Keyword(s):

Excited State ◽

Organic Dye ◽

Relaxation Processes ◽

Dye Molecules ◽

Excited State Lifetime ◽

Molecular Relaxation ◽

Relaxation Transitions ◽

Theoretical Investigations ◽

Excited State Population ◽

Viscosity Dependence

The dependence of excited-state lifetime, fluorescence quantum yield and isomerization rate of organic dye molecules on solvent viscosity has been a subject of numerous experimental and theoretical investigations. To explain the viscosity dependence of excited-state lifetime in this paper the temporal behavior of the excited state population is calculated for several models of the molecular relaxation process by a computer simulation incorporating both the stochastical motion of large molecular parts in the excited state and relaxation transitions. The described method is applicable to calculating the probability of changing the electronic state as a function of time and internal rotation coordinate.

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Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd3(dppm)3CO2+ catalyst

Canadian Journal of Chemistry ◽

10.1139/v95-019 ◽

1995 ◽

Vol 73 (1) ◽

pp. 123-130 ◽

Cited By ~ 7

Author(s):

Pierre D. Harvey ◽

Marielle Crozet ◽

Khin T. Aye

Keyword(s):

Excited State ◽

Ground State ◽

Flash Photolysis ◽

Excited State Lifetime ◽

Metal Atoms ◽

Uv Visible ◽

Low Efficiency ◽

Solvent Molecules ◽

Host Chemistry ◽

Electron Cluster

The photoinduced addition of O2 onto the unsaturated cluster Pd3(dppm)3CO2+ (as a CF3CO2− salt) in acetonitrile is reported. The final product Pd3(dppm)3(O2)22+(v(O2) = 838 and 866 cm−1) is formed in a multi-step fashion in which two photochemical intermediates are observed (presumably Pd3(dppm)3(O2)(CO)2+ and Pd3(dppm)3(O2)2+. No X-ray structure could be obtained, but numerous spectroscopic findings demonstrate that O2 binds the Pd3 center as a peroxo-O2, and acts as a two-electron donor that triply bridges the metal atoms (forming a 44-electron cluster). The very small excited state lifetimes (between 25 and 35 ± 10 ps) obtained by picosecond flash photolysis indicate that the primary photoreaction is unimolecular, and demonstrate that the first photochemically added O2 molecule must be preassembled in the excited state prior to any photoinduced transformation. This [Formula: see text] ground state complex is responsible for the photoinduced production of the bisdioxygen compound and can be observed by UV–visible spectroscopy. The low efficiency of the photoreaction (quantum yield (Φ) = 0.033 ± 0.004) is explained by the very short excited state lifetime at 298 K, and the competition of O2 with solvent molecules to occupy the unsaturated site of the empty cavity in Pd3(dppm)3CO2+ (i.e., ground state guest–host chemistry). The binding constant for O2 with Pd3(dppm)3CO2+ is roughly estimated to range between 1 and 730 M−1 in the ground state and is considered to be weak. Keywords: clusters, photochemistry, guest–host, oxidation, dioxygen.

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Renilla Bioluminescence: A Morphologic Approach to the Location of Photocytes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100051050 ◽

1974 ◽

Vol 32 ◽

pp. 208-209

Author(s):

Ben O. Spurlock ◽

Milton J. Cormier

Keyword(s):

Excited State ◽

Ground State ◽

Molecular Basis ◽

Light Emission ◽

Chemical Basis ◽

Electronic Excited State ◽

Colonial Form ◽

The Common ◽

Eighteenth And Nineteenth Centuries ◽

Catalyzed Oxidation

The phenomenon of bioluminescence has fascinated layman and scientist alike for many centuries. During the eighteenth and nineteenth centuries a number of observations were reported on the physiology of bioluminescence in Renilla, the common sea pansy. More recently biochemists have directed their attention to the molecular basis of luminosity in this colonial form. These studies have centered primarily on defining the chemical basis for bioluminescence and its control. It is now established that bioluminescence in Renilla arises due to the luciferase-catalyzed oxidation of luciferin. This results in the creation of a product (oxyluciferin) in an electronic excited state. The transition of oxyluciferin from its excited state to the ground state leads to light emission.

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Ground State and Excited State H-Atom Temperatures in a Microwave Plasma Diamond Deposition Reactor

Journal de Physique III ◽

10.1051/jp3:1996176 ◽

1996 ◽

Vol 6 (9) ◽

pp. 1167-1180 ◽

Cited By ~ 25

Author(s):

A. Gicquel ◽

M. Chenevier ◽

Y. Breton ◽

M. Petiau ◽

J. P. Booth ◽

...

Keyword(s):

Excited State ◽

Ground State ◽

Microwave Plasma ◽

Diamond Deposition

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Spin-Forbidden Excitation Enables Infrared Photoredox Catalysis

10.26434/chemrxiv.12124215.v1 ◽

2020 ◽

Author(s):

Tomislav Rovis ◽

Benjamin D. Ravetz ◽

Nicholas E. S. Tay ◽

Candice Joe ◽

Melda Sezen-Edmonds ◽

...

Keyword(s):

Excited State ◽

Ground State ◽

Intersystem Crossing ◽

Photoredox Catalysis ◽

Infrared Irradiation ◽

Triplet Excitation ◽

New Family ◽

Ir Light

We describe a new family of catalysts that undergo direct ground state singlet to excited state triplet excitation with IR light, leading to photoredox catalysis without the energy waste associated with intersystem crossing. The finding allows a mole scale reaction in batch using infrared irradiation.

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Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

10.26434/chemrxiv.7860023 ◽

2019 ◽

Author(s):

Matthew M. Brister ◽

Carlos Crespo-Hernández

Keyword(s):

Excited State ◽

Excited States ◽

Ground State ◽

Transient Absorption ◽

Electronic Energy ◽

Transient Absorption Spectroscopy ◽

Electronic Relaxation ◽

Vibrationally Excited ◽

Excited State Dynamics ◽

Π State

Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived 1nOπ* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived 3ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.

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Impact of the Dynamic Electron Correlation on the Unusually Long Excited-State Lifetime of Thymine

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.1c00712 ◽

2021 ◽

pp. 4339-4346

Author(s):

Woojin Park ◽

Seunghoon Lee ◽

Miquel Huix-Rotllant ◽

Michael Filatov ◽

Cheol Ho Choi

Keyword(s):

Excited State ◽

Electron Correlation ◽

Excited State Lifetime

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Mechanistic analysis of light-driven overcrowded alkene-based molecular motors by multiscale molecular simulations

Physical Chemistry Chemical Physics ◽

10.1039/d0cp06685k ◽

2021 ◽

Vol 23 (14) ◽

pp. 8525-8540

Author(s):

Mudong Feng ◽

Michael K. Gilson

Keyword(s):

Molecular Dynamics ◽

Excited State ◽

Molecular Dynamics Simulations ◽

Ground State ◽

Molecular Motors ◽

Motor Performance ◽

Molecular Simulations ◽

Mechanistic Analysis ◽

Dynamics Simulations ◽

Shed Light

Ground-state and excited-state molecular dynamics simulations shed light on the rotation mechanism of small, light-driven molecular motors and predict motor performance. How fast can they rotate; how much torque and power can they generate?

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